The distillation of a mixture of hydrocarbons



Patented June 7, 1949 THE DISTILLATION OF A MIXTURE OF HY DROCARBON S Richard 0. Brandon, Elizabeth, and Minor 0. K.

J ones, Mountainside, N. J assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application May 5, 1 945,

SerialNo. 592,272

4 Claims.

This invention relates to improvements in the distillation of low-boiling hydrocarbons and, particularly, to the distillation of low-boiling hydrocarbons obtained by cracking or catalytic reforming of petroleum hydrocarbons.

Cracking petroleum oils under severe conditions, particularly at high temperatures and low pressures, with or without the presence of steam, produces distillates containing a large proportion of unsaturated hydrocarbons. These unsaturate's present, especially conjugated dfolefins, render the distillates unstable, and they are" easily oxidized with consequent loss in octane rating and excessive formation of gum. v

In general, there are several methods known in the art of petroleum refining by which unstable distillates can be rendered satisfactory for use. In some cases, the addition of an antioxidant is sufficient; however, in gasolines obtained by extremely high temperature and low pressure cracking or in steam cracked gasoline,

even large amounts of the most powerful antioxidants have practically no effect. Treating with strong sulfuric acid is satisfactory for many distillates, but with high temperature low pressure cracked or steam cracked gasolines the acid consumption is high, treating losses are excessive, and gum or storage stability of the treated distillate is sometimes questionable. A satisfactory method for stabilizing steam cracked gasoline is treatment with hot clay in the vapor phase. This process requires extensiveequipment with consequent installation and operating costs. Therefore, it is very desirable to have a process by which unstable distillates may be refined which does not require additional equipment and for which operating costs would be comparatively low.

According to the present invention unstable distillates, containing unsaturated hydrocarbons obtained by cracking at high temperatures and low pressure, for example, steam cracked gasolines, are refined by distillation over phenolic substances in the presence of traces of sulfuric or sulfonic acids. Under conditions of distillation, the unstable hydrocarbons condense with phenols and remain as bottoms while the overhead product is extremely stable. Sulfuric acid or aromatic sulfonic acids catalyze the condensation of un'saturatcs with phenols, and the amount required is very small, though in the absence of the acid, condensation is negligible. Phenol can be used to remove unstable material, but this substance is expensive. Higher homologs of phenol, such as phenolic materials extracted from heavy petroleum distillates, serve equally well and are readily available at much lower cost.

As an example of the results which can be obtained by the proposed process, a sample of steam cracked gasoline Was distilled over 25% of petroleum phenols, and a second sample was distilled over 25% of petroleum phenols containing a trace of sulfuric acid. Distillate from the second operation was appreciably more stable as shown by the following inspections:

.0assistancecheatat and Since a breakdown of at least I- minutes and a maximum copper dish gum of 20 should be required of a stable gasoline, it is apparent that the process described in this application gives a satisfactory product.

A sample of steam cracked gasoline produced at approximately 1200 F. was mixed with onefourth its volume of petroleum phenols and divided into two portions; the first was distilled over a small amount of benzene sulfonic acid, and the second, over sulfuric acid. After caustic washing, distillates from both tests were found to be of satisfactory stability and were approximately the same as gasoline produced by clay treating similar distillate.

A comparison is shown in the following table:

4 with about one-fourth its volume of petroleum phenols and an acid catalyst consisting of sul- Charge to Still:

Gasoline, ml Petroleum Phenols, m Catalyst Wt. of Catalyst, grams Feed Gasoline Yield, Vol. per cent 100. Gasoline Inspections:

Breakdownuninhibited.. Copper Dish Gum-uninhibited Breakdown with 5 rug/100 ml. of a solution oip-ammophenol 1 50 Copper Dish Gum with 5 mg./100 ml. of a solution of p-arnino-phenol 1 399 Bromine N o.cg./g 163 Diene No.cg./g 25. Conjugated Diolefins Wt. Per Cent (estimated) 15.0 Suliur, Wt. Per Cent 0.034 Octane No.2

ASTM-Cle 79. AS'llV Glear+3 ml./gal. Tetra/ethyl lead.. 81. 9 Co-operative Fuel Research (1939)-Clear 95. 1 Co-operative Fuel Research (l939)-Clear+3 mL/gal.

Tetracthyl lead 97. 6

3, 200 3, 200 800 800 Benzene sulfonic acid H 804 (Clay Treated) 1 A solution of 50% p-amino-phenol, 30% isopropyl alcohol and. 20% anhydrous methyl alcohol being used.

These data show clearly that steam cracked distillates can be stabilized by the process suggested. Yields and product quality are similar to those obtained by clay treating, which is the method currently used.

Since petroleum phenols are of value, they should be recovered after use for stabilizing gasoline as just described and this can be accomplished readily by thermal or catalytic cracking. In the present work, residual alkylated phenols from refining steam cracked distillate were cracked at 950 F. and atmospheric pressure in the presence of a synthetic silica-alumina catalyst. In this single-pass operation, 86% of the original petroleum phenols were recovered boiling 400-585 F. With recycle of the unconverted material, even higher recoveries should be possible. Accordingly, the phenols may be recovered and recycled for use in treating additional quantities of gasoline.

It is not intended that the method should be limited to steam cracked distillates nor to gasolines. Other unstable distillates, such as those obtained by severe thermal cracking or reforming, can be readily treated, and distillates boiling above the asoline range, such as heating oil fractions, can be stabilized by the proposed process.

We claim:

1. A method of distilling cracked gasoline which consists of the steps of mixing gasoline containing gum forming unsaturated hydrocarbons with about one-fourth its volume of petroleum phenols and an acid catalyst selected from the class consisting of sulfuric acid and aromatic sulfonic acid and recovering overhead a gasoline of substantially greater storage stability.

2. A method of distilling cracked gasoline which consists of the steps of mixing gasoline containing gum forming unsaturated hydrocarbons furic acid and recovering overhead a gasoline of substantially greater storage stability.

3. A method of distilling cracked gasoline which consists of the steps of mixing gasoline containing gum formin unsaturated hydrocarbons with about one-fourth its volume of petroleum phenols and an acid catalyst consisting of aromatic sulfonic acid and recovering overhead a gasoline of substantially greater storage stability.

4. A method of distilling cracked gasoline which consists of the steps of mixing gasoline containing gum forming unsaturated hydrocarbons with about one-fourth its volume of petroleum phenols and an acid catalyst selected from the class consisting of sulfuric acid and aromatic sulfonic acid, recovering overhead a gasoline of substantially greater storage stability, and cracking residual alkylated phenols in the presence of a synthetic silica-alumina catalyst whereby the original petroleum phenols may be recovered to be recycled to the said mixing step.

RICHARD C. BRANDON. MINOR C. K. JONES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,814,410 Richter et al July 14, 1931 2,001,634 Stevens et a1 May 14, 1935 2,017,610 Stevens et al Oct. 15, 1935 2,061,583 Malisofi et a1 Nov. 24, 1936 2,152,166 Yabroff Mar. 28, 1939 2,200,703 Retailliau May 14, 1940 2,212,805 Zinke Aug. 27, 1940 2,228,028 Brower Jan. 7, 1941 

